Supermarkets, led by Hugh Fearnley-Whittingstall's Fish Fight and Sainsbury's Switch the Fish campaigns, have recently been encouraging us to eat lesser-known and so-called sustainable fish species in a bid to make more sustainable choices.

What they haven't told you is that the majority of fish sold in UK supermarkets is already from sustainable sources such as Iceland, the Barents Sea, or from the Baltic.

And that's not the only problem with this well-meaning campaign. The market for fish is now a global business and fish wholesalers are able to find other outlets for threatened species such as cod, haddock and monkfish. If the UK market won't buy the fish someone else will.

By encouraging us to eat less popular fish species such as mackerel, megrim, pouting, gurnard, coley or dab, all that will be achieved is to increase the market for fish. And this is already happening with overall sales of fish at supermarkets hitting record levels. In the weeks after the Fish Fight campaign was launched Marks & Spencer and Waitrose reported increased fish sales of 25% and 15%.

If we are seriously going to tackle the problem of overfishing then people are going to have to eat less fish, fishermen are going to have to catch less fish, and supermarkets will have to sell less fish. Creating a whole new market for previously unpopular species is just spreading the problem not solving it.